Electrolyte solution for secondary batteries, and secondary battery

Abstract

The present invention provides a secondary battery which is capable of achieving excellent battery characteristics and excellent safety. This secondary battery is provided with a positive electrode, a negative electrode, and an electrolyte solution that contains a solvent. The solvent contains an anisole compound represented by formula (1), and the content of the anisole compound in the solvent is 30% by weight or more.

Description

Electrolyte for secondary battery and secondary battery

[0001] The present technology relates to an electrolyte for a secondary battery and a secondary battery.

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as small, lightweight power sources that can provide high energy density. These secondary batteries contain a positive electrode, a negative electrode, and an electrolyte solution, and various studies have been conducted on the configuration of these secondary batteries.

[0003] Specifically, the non-aqueous electrolyte solution contains a fluorine-containing organic compound, and the content of the fluorine-containing organic compound in the non-aqueous electrolyte solution is 0.01% by weight to 20% by weight (see, for example, Patent Document 1). Also, the electrolyte solution contains dimethoxyethane and anisole, and the mixture ratio (molar ratio) of the dimethoxyethane and the anisole is 1:2 (see, for example, Non-Patent Document 1).

[0004] Patent No. 4127355

[0005] Nature Communications, volume 13, Article number: 4538, 2022

[0006] Although various studies have been conducted on the configuration of secondary batteries, the battery characteristics and safety of the secondary batteries are still insufficient, and there is room for improvement.

[0007] There is a demand for an electrolyte solution for a secondary battery and a secondary battery that can provide excellent battery characteristics and excellent safety.

[0008] According to one embodiment of the present technology, there is provided an electrolyte solution for a secondary battery, which contains a solvent, the solvent contains an anisole compound represented by formula (1), and the content of the anisole compound in the solvent is 30 wt % or more.

[0009] (R1, R2, and R3 are each either a hydrogen group or a halogen group.)

[0010] A secondary battery according to an embodiment of the present technology includes a positive electrode, a negative electrode, and an electrolyte, and the electrolyte has a configuration similar to that of the electrolyte for a secondary battery according to the embodiment of the present technology described above.

[0011] As shown in formula (1), the anisole compound has a trifluoromethoxy group (-OCF 3　 ) and a methoxy group (-OCR1R2R3) bonded to a benzene ring. However, the positions at which the trifluoromethoxy group and the methoxy group are bonded to the benzene ring are not particularly limited. The details of the structure of the anisole compound will be described later.

[0012] According to the electrolyte solution for a secondary battery or the secondary battery of an embodiment of the present technology, the solvent contains the anisole compound represented by formula (1), and the content of the anisole compound in the solvent is 30 wt % or more, so that excellent battery characteristics and excellent safety can be obtained.

[0013] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below.

[0014] Fig. 1 is a perspective view illustrating a configuration of a secondary battery according to an embodiment of the present technology. Fig. 2 is an enlarged cross-sectional view illustrating the configuration of a battery element illustrated in Fig. 1. Fig. 3 is a block diagram illustrating the configuration of an application example of the secondary battery.

[0015] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be made in the following order: 1. Electrolyte for secondary battery 1-1. Configuration 1-2. Manufacturing method 1-3. Action and effect 2. Secondary battery 2-1. Configuration 2-2. Operation 2-3. Manufacturing method 2-4. Action and effect 3. Modification 4. Use of secondary battery

[0016] 1. Electrolyte for Secondary Battery First, an electrolyte for a secondary battery (hereinafter simply referred to as "electrolyte") according to an embodiment of the present technology will be described.

[0017] This electrolytic solution is a liquid electrolyte used in a secondary battery, which is an electrochemical device. However, the electrolytic solution may also be used in other electrochemical devices. The type of other electrochemical device is not particularly limited, but specifically, it may be a capacitor or the like.

[0018] <1-1. Structure> The electrolytic solution contains a solvent. More specifically, the electrolytic solution further contains an electrolyte salt that ionizes in the solvent.

[0019] [Solvent] The solvent is a medium for dissolving and ionizing the electrolyte salt. The solvent used here is a non-aqueous solvent, and therefore the electrolyte solution containing the non-aqueous solvent is a so-called non-aqueous electrolyte solution.

[0020] (Anisole Compound) The solvent contains one or more of the anisole compounds represented by formula (1).

[0021] (R1, R2, and R3 are each either a hydrogen group or a halogen group.)

[0022] As described above, this anisole compound has a trifluoromethoxy group (-OCF 3　 ) and a methoxy-type group (—OCR1R2R3) bonded to a benzene ring. However, there are no particular limitations on the positions at which the trifluoromethoxy group and the methoxy-type group are bonded to the benzene ring.

[0023] Therefore, when the position at which the trifluoromethoxy group is bonded to the benzene ring is used as a reference, the methoxy-type group may be positioned at the ortho position relative to the trifluoromethoxy group, the meta position relative to the trifluoromethoxy group, or the para position relative to the trifluoromethoxy group.

[0024] As described above, each of R1 to R3 is either a hydrogen group or a halogen group. The types of R1 to R3 may be the same or different from one another. Of course, any two types of R1 to R3 may be the same.

[0025] The type of halogen group is not particularly limited, but specific examples include a fluorine group, a chlorine group, a bromine group, and an iodine group.

[0026] Specific examples of the anisole compound include 2-(trifluoromethoxy)anisole (R1=R2=R3=hydrogen groups), 3-(trifluoromethoxy)anisole (R1=R2=R3=hydrogen groups), 4-(trifluoromethoxy)anisole (R1=R2=R3=hydrogen groups), and 4-(trifluoromethoxy)trifluoroanisole (R1=R2=R3=fluorine groups).

[0027] However, the content of the anisole compound in the solvent is set to a predetermined amount, specifically, the content of the anisole compound in the solvent is 30% by weight or more.

[0028] The solvent contains an anisole compound, and the content of the anisole compound in the solvent is 30% by weight or more because this ensures safety during use of a secondary battery using the electrolyte solution while suppressing the decomposition reaction of the electrolyte solution during charging and discharging of the secondary battery.

[0029] Specifically, anisole compounds have a property of being less likely to coordinate with alkali metal ions than other compounds described below. These alkali metal ions are alkali metal ions derived from cations contained in the electrolyte salt, more specifically, lithium ions described below. As a result, in the electrolyte solution, other compounds tend to coordinate with alkali metal ions, whereas anisole compounds tend not to coordinate with alkali metal ions.

[0030] It is known that other compounds that coordinate with alkali metal ions are more susceptible to reductive decomposition than other compounds that do not coordinate with alkali metal ions. The tendency regarding the reductive decomposition of other compounds described here is also observed in the anions contained in the electrolyte salt. In contrast, anisole compounds, as described above, are less likely to coordinate with alkali metal ions and are therefore less susceptible to reductive decomposition.

[0031] Therefore, while the other compounds and anions are each susceptible to reductive decomposition, the anisole compound is less susceptible to reductive decomposition. Therefore, by changing the types of the other compounds and anions, it is possible to adjust the electrochemical state of the coating film, which will be described later, formed on the surface of the negative electrode.

[0032] In addition, the trifluoromethoxy group of the anisole compound contains fluorine as a constituent element. As a result, when the anisole compound is decomposed during charging and discharging of the secondary battery, a good coating containing fluorine as a constituent element is easily formed on the surface of the negative electrode, and the surface of the negative electrode is electrochemically protected by the coating. As a result, even if the negative electrode has high reactivity, the decomposition reaction of the electrolyte on the surface of the negative electrode is suppressed.

[0033] Furthermore, anisole compounds have a higher boiling point and a higher flash point than other compounds, which makes it difficult for the electrolyte to boil or flash even if the temperature of the secondary battery rises due to some factor during use of the secondary battery.

[0034] From these points, as described above, the safety of the secondary battery during use is ensured, while the decomposition reaction of the electrolyte during charging and discharging of the secondary battery is suppressed.

[0035] In this case, the content of the anisole compound in the solvent is particularly optimized, so that the protective function of the anisole compound for protecting the surface of the negative electrode is effectively exerted, and the surface of the negative electrode is sufficiently and stably protected by the coating, so that the decomposition reaction of the electrolyte is also sufficiently and stably suppressed.

[0036] In particular, the content of the anisole compound in the solvent is preferably 60% by weight or more, because the protective function of the anisole compound is more effectively exerted, and the decomposition reaction of the electrolyte solution is more effectively suppressed.

[0037] The content of the anisole compound in the solvent is preferably 80% by weight or less, because this ensures the solubility of the electrolyte salt in the electrolyte solution while sufficiently suppressing the decomposition reaction of the electrolyte solution.

[0038] The halogen group preferably contains a fluorine group, because this improves the reactivity of the anisole compound, making it easier to form a coating on the surface of the negative electrode.

[0039] The anisole compound preferably contains a compound represented by formula (2). That is, the methoxy group is preferably positioned para to the trifluoromethoxy group. This is because the reactivity of the anisole compound is improved, making it easier to form a coating on the surface of the negative electrode. Details regarding R4 to R6 are the same as those regarding R1 to R3.

[0040] (Each of R4, R5, and R6 is either a hydrogen group or a halogen group.)

[0041] As described above, specific examples of the compound represented by formula (2) include 4-(trifluoromethoxy)anisole (R4, R5, and R6 are hydrogen groups) and 4-(trifluoromethoxy)trifluoroanisole (R4, R5, and R6 are fluorine groups).

[0042] Furthermore, the anisole compound preferably contains 4-(trifluoromethoxy)anisole, because the protective function of the anisole compound is sufficiently exhibited, and the decomposition reaction of the electrolyte is also sufficiently suppressed.

[0043] In order to confirm that the solvent contains an anisole compound and to measure the content of the anisole compound in the solvent, the electrolyte is analyzed by any method, including, but not limited to, one or more of inductively coupled plasma (ICP) atomic emission spectroscopy, nuclear magnetic resonance spectroscopy (NMR), and gas chromatography-mass spectrometry (GC-MS).

[0044] When a secondary battery containing the electrolyte is used to analyze the electrolyte, the secondary battery is disassembled to recover the electrolyte, and the electrolyte is then analyzed, thereby identifying the type of component (anisole compound) contained in the electrolyte and the content of the component.

[0045] (Other Compounds) The solvent may further contain one or more of the other compounds. As is clear from the range of the content of the anisole compound in the solvent described above, the solvent may contain other compounds in addition to the anisole compound.

[0046] The other compounds are non-aqueous solvents (organic solvents), except that the above-mentioned anisole compounds are excluded from the other compounds described here.

[0047] The non-aqueous solvent is an ester, an ether, or the like, more specifically, a carbonate ester compound, a carboxylic acid ester compound, a lactone compound, or the like, because it improves the dissociation of the electrolyte salt and also improves the mobility of ions.

[0048] The carbonate ester compounds include cyclic carbonate esters and chain carbonate esters, etc. Specific examples of cyclic carbonate esters include ethylene carbonate and propylene carbonate, and specific examples of chain carbonate esters include dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0049] The carboxylic acid ester compound is a chain carboxylic acid ester, etc. Specific examples of the chain carboxylic acid ester include ethyl acetate, ethyl propionate, propyl propionate, and ethyl trimethylacetate.

[0050] The lactone compound is lactone, etc. Specific examples of lactone include γ-butyrolactone and γ-valerolactone.

[0051] The ethers may be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, anisole, or the like.

[0052] The non-aqueous solvent may be an unsaturated cyclic carbonate, a fluorinated cyclic carbonate, a sulfonate, a phosphate, an acid anhydride, a nitrile compound, an isocyanate compound, or the like, because the electrochemical stability of the electrolyte solution is improved.

[0053] Specific examples of unsaturated cyclic carbonates include vinylene carbonate, vinylethylene carbonate, and methyleneethylene carbonate. Specific examples of fluorinated cyclic carbonates include monofluoroethylene carbonate and difluoroethylene carbonate. Specific examples of sulfonic acid esters include propane sultone and propene sultone. Specific examples of phosphate esters include trimethyl phosphate and triethyl phosphate. Specific examples of acid anhydrides include succinic anhydride, 1,2-ethanedisulfonic anhydride, and 2-sulfobenzoic anhydride. Specific examples of nitrile compounds include succinonitrile. Specific examples of isocyanate compounds include hexamethylene diisocyanate.

[0054] [Electrolyte Salt] The electrolyte salt contains one or more types of light metal salts such as lithium salts.

[0055] A specific example of the lithium salt is lithium hexafluorophosphate (LiPF 6　 ), lithium tetrafluoroborate (LiBF 4　 ), lithium trifluoromethanesulfonate (LiCF 3　 SO 3　 ), lithium bis(fluorosulfonyl)imide (LiN(FSO 2　 ) 2　 ), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF 3　 SO 2　 ) 2　 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF 3　 SO 2　 ) 3　 ), lithium bis(oxalato)borate (LiB(C 2　 O 4　 ) 2　 ), lithium monofluorophosphate (Li 2　 PFO 3　 ) and lithium difluorophosphate (LiPF 2　 O 2　 ) etc. This is because a high battery capacity can be obtained.

[0056] The content of the electrolyte salt is not particularly limited, but specifically, it is 0.3 mol / kg to 3.0 mol / kg relative to the solvent, because high ionic conductivity can be obtained.

[0057] <1-2. Manufacturing Method> When manufacturing an electrolytic solution, an electrolyte salt is added to a solvent containing an anisole compound. In this case, the amount of the anisole compound added is adjusted so that the content of the anisole compound in the solvent falls within the above-mentioned range. This dissolves the electrolyte salt in the solvent, thereby preparing an electrolytic solution.

[0058] <1-3. Actions and Effects> In this electrolytic solution, the solvent contains an anisole compound, and the content of the anisole compound in the solvent is 30% by weight or more.

[0059] In this case, as described above, the properties of the anisole compound are utilized to make it difficult for the anisole compound to coordinate with alkali metal ions, and a good coating containing fluorine as a constituent element is easily formed on the surface of the negative electrode during charge and discharge of the secondary battery using the electrolyte, thereby electrochemically protecting the surface of the negative electrode using the coating, and suppressing the decomposition reaction of the electrolyte on the surface of the negative electrode.

[0060] Furthermore, as described above, by utilizing the properties of the anisole compound, even if the temperature of a secondary battery containing an electrolyte rises due to some factor during use, the electrolyte is less likely to boil or catch fire.

[0061] From these points, safety during use of a secondary battery using an electrolytic solution is ensured, while the decomposition reaction of the electrolytic solution is suppressed during charging and discharging of the secondary battery, thereby realizing a secondary battery with excellent battery characteristics and excellent safety.

[0062] In particular, if the content of the anisole compound in the solvent is 60% by weight or more, the decomposition reaction of the electrolyte can be further suppressed by utilizing the protective function of the anisole compound, and therefore a higher effect can be obtained.

[0063] Furthermore, if the content of the anisole compound in the solvent is 80% by weight or less, the solubility of the electrolyte salt in the electrolyte solution is ensured while the decomposition reaction of the electrolyte solution is sufficiently suppressed, thereby achieving a higher effect.

[0064] Furthermore, if the halogen group contains a fluorine group, the reactivity of the anisole compound is improved, which makes it easier to form a coating on the surface of the negative electrode, thereby achieving a greater effect.

[0065] Furthermore, if the anisole compound contains the compound represented by formula (2), the reactivity of the anisole compound is improved, which makes it easier to form a coating on the surface of the negative electrode, thereby achieving a greater effect.

[0066] Furthermore, if the anisole compound contains 4-(trifluoromethoxy)anisole, the protective function of the anisole compound is fully exerted, and therefore the decomposition reaction of the electrolyte is also sufficiently suppressed, resulting in a higher effect.

[0067] 2. Secondary Battery Next, a secondary battery using the above-described electrolytic solution will be described.

[0068] The secondary battery described here is a secondary battery that obtains battery capacity by utilizing the absorption and desorption of electrode reactants, and is equipped with a positive electrode, a negative electrode, and an electrolyte.

[0069] The type of electrode reactant is not particularly limited, but specifically includes light metals such as alkali metals and alkaline earth metals. Specific examples of alkali metals include lithium, sodium, and potassium, and specific examples of alkaline earth metals include beryllium, magnesium, and calcium.

[0070] In the following, we will take the case where the electrode reactant is lithium as an example. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is called a lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and desorbed in the ionic state.

[0071] In a lithium-ion secondary battery, the charge capacity of the negative electrode is preferably larger than the discharge capacity of the positive electrode. That is, the electrochemical capacity per unit area of ​​the negative electrode is preferably larger than the electrochemical capacity per unit area of ​​the positive electrode. This is to prevent deposition of electrode reactants on the surface of the negative electrode during charging.

[0072] 2-1. Structure FIG. 1 shows a perspective view of the secondary battery, and FIG. 2 shows an enlarged cross-sectional view of the battery element 20 shown in FIG.

[0073] 1 shows a state in which the exterior film 10 and the battery element 20 are separated from each other, and a cross section of the battery element 20 taken along the XZ plane is shown by a broken line. In FIG. 2, only a part of the battery element 20 is shown.

[0074] As shown in FIGS. 1 and 2, this secondary battery includes an exterior film 10, a battery element 20, a positive electrode lead 31, a negative electrode lead 32, and sealing films 41 and .

[0075] As described above, the secondary battery described here uses flexible or pliable exterior film 10 as an exterior member for housing battery element 20. Therefore, the secondary battery shown in Figures 1 and 2 is a so-called laminate film type secondary battery.

[0076] 1, the exterior film 10 has a bag-like structure that is sealed when the battery element 20 is housed therein. As a result, the exterior film 10 houses a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte solution (not shown), which will be described later.

[0077] Here, the exterior film 10 is a single film-like member that is folded in a folding direction F. The exterior film 10 is provided with a recessed portion 10U (a so-called deep drawn portion) for accommodating the battery element 20.

[0078] Specifically, the exterior film 10 is a three-layer laminate film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order from the inside out, and when the exterior film 10 is folded, the outer peripheral edges of the opposing fusion layers are fused to each other. The fusion layer contains a polymer compound such as polypropylene. The metal layer contains a metal material such as aluminum. The surface protection layer contains a polymer compound such as nylon.

[0079] However, the configuration (number of layers) of the exterior film 10 is not particularly limited, and may be one layer, two layers, or four or more layers.

[0080] [Battery Element] The battery element 20 is housed in an exterior film 10. This battery element 20 is a so-called power generation element, and as shown in Figures 1 and 2, includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte (not shown).

[0081] Here, battery element 20 is a so-called wound electrode body, and therefore positive electrode 21 and negative electrode 22 are wound around winding axis P while facing each other with separator 23 interposed therebetween. This winding axis P is a virtual axis extending in the Y-axis direction, as shown in FIG.

[0082] There are no particular limitations on the three-dimensional shape of battery element 20. Here, battery element 20 has a flat three-dimensional shape, and therefore the shape of a cross section (cross section along the XZ plane) of battery element 20 intersecting winding axis P is a flat shape defined by major axis J1 and minor axis J2.

[0083] The major axis J1 is an imaginary axis extending in the X-axis direction and has a length greater than that of the minor axis J2. The minor axis J2 is an imaginary axis extending in the Z-axis direction intersecting the X-axis direction and has a length less than that of the major axis J1. Here, the three-dimensional shape of the battery element 20 is a flattened cylinder, and therefore the cross-sectional shape of the battery element 20 is a flattened, approximately elliptical shape.

[0084] (Positive Electrode) As shown in Fig. 2, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B. However, the positive electrode current collector 21A may be omitted.

[0085] The positive electrode current collector 21A has a pair of surfaces on which the positive electrode active material layer 21B is provided. The positive electrode current collector 21A contains a conductive material such as a metal material, and a specific example of the conductive material is aluminum.

[0086] The positive electrode active material layer 21B contains one or more types of positive electrode active materials that absorb and release lithium. However, the positive electrode active material layer 21B may further contain one or more types of other materials such as a positive electrode binder and a positive electrode conductive agent. The method for forming the positive electrode active material layer 21B is not particularly limited, but specifically includes a coating method.

[0087] Here, the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A. However, the positive electrode active material layer 21B may be provided on only one side of the positive electrode current collector 21A, on the side where the positive electrode 21 faces the negative electrode 22.

[0088] The type of positive electrode active material is not particularly limited, but specifically includes a lithium-containing compound. This lithium-containing compound is a compound containing lithium and one or more transition metal elements as constituent elements, and may further include one or more other elements as constituent elements. The type of other element is not particularly limited as long as it is an element other than lithium and transition metal elements, but specifically includes elements belonging to Groups 2 to 15 of the long period periodic table. The type of lithium-containing compound is not particularly limited, but specifically includes oxides, phosphate compounds, silicate compounds, borate compounds, and the like.

[0089] A specific example of the oxide is LiNiO 2　 , LiCoO 2　 , LiCo 0.98 Al 0.01 Mg 0.01 O 2　 , LiNi 0.5　 Co 0.2　 Mn 0.3　 O 2　 , LiNi 0.8　 Co 0.15 Al 0.05 O 2　 , LiNi 0.33 Co0.33 Mn 0.33 O 2　 , Li 1.2　 Mn 0.52 Co 0.175　 Ni 0.1　 O 2　 , Li 1.15 (Mn 0.65 Ni 0.22 Co 0.13 ) O 2　 and LiMn 2　 O 4　 Specific examples of phosphate compounds include LiFePO 4　 , LiMnPO 4　 , LiFe 0.5　 Mn 0.5　 P.O. 4　 and LiFe 0.3　 Mn 0.7　 P.O. 4　 And so on.

[0090] The positive electrode binder contains one or more of materials such as synthetic rubber and polymer compounds. Specific examples of synthetic rubber include styrene-butadiene rubber, fluorine-containing rubber, and ethylene-propylene-diene. Specific examples of polymer compounds include polyvinylidene fluoride, polyimide, and carboxymethyl cellulose.

[0091] The positive electrode conductive agent contains one or more conductive materials such as a carbon material, a metal material, and a conductive polymer compound, and specific examples of the carbon material include graphite, carbon black, acetylene black, and ketjen black.

[0092] (Negative Electrode) The negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B, as shown in Fig. 2. However, the negative electrode current collector 22A may be omitted.

[0093] The negative electrode current collector 22A has a pair of surfaces on which the negative electrode active material layer 22B is provided. The negative electrode current collector 22A contains a conductive material such as a metal material, and a specific example of the conductive material is copper.

[0094] The negative electrode active material layer 22B includes one or more types of negative electrode active materials that absorb and release lithium. However, the negative electrode active material layer 22B may further include one or more types of other materials, such as a negative electrode binder and a negative electrode conductive agent. The method for forming the negative electrode active material layer 22B is not particularly limited, and specifically includes one or more types of a coating method, a vapor phase method, a liquid phase method, a thermal spraying method, and a firing method (sintering method).

[0095] Here, the anode active material layer 22B is provided on both sides of the anode current collector 22A. However, the anode active material layer 22B may be provided on only one side of the anode current collector 22A on the side where the anode 22 faces the cathode 21.

[0096] The type of negative electrode active material is not particularly limited, but specific examples include carbon materials and metal-based materials, because high energy density can be obtained.

[0097] Specific examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite, etc. The graphite may be natural graphite, artificial graphite, or both.

[0098] Metallic materials are a general term for materials containing one or more of metal elements and semi-metal elements that can form an alloy with lithium as constituent elements, and specific examples of the metal elements and semi-metal elements include silicon and tin. This metallic material may be a simple substance, an alloy, a compound, a mixture of two or more of these, or a material containing two or more of these phases. However, the simple substance may contain any amount of impurities. A specific example of a metallic material is TiSi 2　 and SiO x　 (0<x≦2 or 0.2<x<1.4), etc.

[0099] The details regarding the negative electrode binder are the same as those regarding the positive electrode binder, and the details regarding the negative electrode conductive agent are the same as those regarding the positive electrode conductive agent.

[0100] 2, the separator 23 is an insulating porous film interposed between the positive electrode 21 and the negative electrode 22, and allows lithium to pass through in an ionic state while preventing the occurrence of a short circuit due to contact between the positive electrode 21 and the negative electrode 22. The separator 23 contains one or more insulating polymer compounds, and a specific example of the insulating polymer compound is polyethylene.

[0101] (Electrolyte) The electrolyte is impregnated into each of the positive electrode 21, the negative electrode 22, and the separator 23, and has the above-described configuration. That is, the solvent contains an anisole compound, and the content of the anisole compound in the solvent is in the above-described range.

[0102] 1 and 2, the positive electrode lead 31 is a positive electrode wiring connected to the positive electrode current collector 21A of the positive electrode 21, and is led out of the exterior film 10. The positive electrode lead 31 contains one or more types of conductive materials such as metal materials, and a specific example of the conductive material is aluminum. The positive electrode lead 31 has a shape such as a thin plate or a mesh.

[0103] [Negative Electrode Lead] As shown in FIGS. 1 and 2 , the negative electrode lead 32 is a negative electrode wiring connected to the negative electrode 22, and is led out of the exterior film 10. Here, the lead-out direction of the negative electrode lead 32 is the same as the lead-out direction of the positive electrode lead 31. The negative electrode lead 32 contains one or more types of conductive materials such as metal materials, and a specific example of the conductive material is copper. The details regarding the shape of the negative electrode lead 32 are the same as the details regarding the shape of the positive electrode lead 31.

[0104] [Sealing Film] As shown in Fig. 1, the sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31. As shown in Fig. 1, the sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32. However, one or both of the sealing films 41, 42 may be omitted.

[0105] The sealing film 41 is a sealing member that prevents outside air and the like from entering the inside of the exterior film 10. This sealing film 41 contains a polymer compound such as polyolefin that has adhesiveness to the positive electrode lead 31, and a specific example of the polymer compound is polypropylene.

[0106] The configuration of the sealing film 42 is the same as the configuration of the sealing film 41, except that the sealing film 42 is a sealing member that has adhesiveness to the negative electrode lead 32. That is, the sealing film 42 contains a polymer compound such as polyolefin that has adhesiveness to the negative electrode lead 32.

[0107] <2-2. Operation> The secondary battery operates in the battery element 20 as follows.

[0108] During charging, lithium is released from the positive electrode 21 and is absorbed into the negative electrode 22 via the electrolyte. During discharging, lithium is released from the negative electrode 22 and is absorbed into the positive electrode 21 via the electrolyte. During both discharging and charging, lithium is absorbed and released in an ionic state.

[0109] <2-3. Manufacturing Method> When manufacturing a secondary battery, the positive electrode 21 and the negative electrode 22 are each produced according to the procedure described below as an example, and then the secondary battery is assembled and subjected to a stabilization process after assembly.

[0110] Since the method for producing the electrolyte solution has already been described, the description of the method for producing the electrolyte solution will be omitted below.

[0111] [Preparation of Positive Electrode] First, a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent are mixed together to form a positive electrode mixture. Then, the positive electrode mixture is poured into a solvent to prepare a paste-like positive electrode mixture slurry. This solvent may be an aqueous solvent or an organic solvent.

[0112] Finally, the cathode mixture slurry is applied to both surfaces of the cathode current collector 21A to form the cathode active material layer 21B. The cathode active material layer 21B may then be compression-molded using a compression device such as a roll press. In this case, the cathode active material layer 21B may be heated, or the compression molding may be repeated multiple times. As a result, the cathode active material layer 21B is formed on both surfaces of the cathode current collector 21A, and the cathode 21 is thus fabricated.

[0113] [Fabrication of Negative Electrode] The negative electrode 22 is formed by the same procedure as the fabrication procedure for the positive electrode 21 described above. Specifically, first, a mixture (negative electrode mixture) of a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent is mixed together and poured into a solvent to prepare a paste-like negative electrode mixture slurry. Details regarding the solvent are as described above. Finally, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 22A to form the negative electrode active material layer 22B. Thereafter, the negative electrode active material layer 22B may be compression-molded. Details regarding compression-molding are as described above. As a result, the negative electrode active material layer 22B is formed on both surfaces of the negative electrode current collector 22A, and the negative electrode 22 is fabricated.

[0114] [Assembly of Secondary Battery] First, the positive electrode lead 31 is connected to the positive electrode current collector 21A of the positive electrode 21 using a joining method such as welding, and the negative electrode lead 32 is connected to the negative electrode current collector 22A of the negative electrode 22 using a joining method such as welding.

[0115] Next, the positive electrode 21 and the negative electrode 22 are stacked together with the separator 23 interposed therebetween to form a laminate (not shown). Next, the laminate is wound to form a wound body (not shown), and then the wound body is pressed using a compression device such as a press to form a flat shape. The wound body after this formation has a configuration similar to that of the battery element 20, except that the positive electrode 21, the negative electrode 22, and the separator 23 are not impregnated with an electrolyte solution.

[0116] Next, after the roll is accommodated in the recess 10U, the exterior film 10 (adhesive layer / metal layer / surface protection layer) is folded to face each other. Next, the outer peripheral edges of two sides of the opposing adhesive layers are joined together using an adhesive method such as heat fusion, thereby accommodating the roll in the bag-shaped exterior film 10.

[0117] Finally, after injecting the electrolyte solution into the bag-shaped exterior film 10, the outer peripheral edges of the remaining sides of the opposing fusion layers are joined together using an adhesive method such as heat fusion. In this case, a sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31, and a sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32.

[0118] This allows the wound body to be impregnated with the electrolyte, thereby producing the battery element 20. The battery element 20 is then sealed in the bag-shaped exterior film 10, thereby assembling the secondary battery.

[0119] [Stabilization Treatment of Assembled Secondary Battery] The assembled secondary battery is charged and discharged. Stabilization conditions such as the ambient temperature, the number of charge / discharge cycles (number of cycles), and charge / discharge conditions can be set arbitrarily.

[0120] As a result, a coating is formed on each surface of the positive electrode 21 and the negative electrode 22. In this case, as described above, a coating derived from the anisole compound is formed on the surface of the negative electrode 22.

[0121] As a result, the state of the battery element 20 becomes electrochemically stable, and the secondary battery is completed.

[0122] <2-4. Actions and Effects> In this secondary battery, the electrolyte has the above-described structure. Therefore, for the reasons described above, safety during use of the secondary battery is ensured, and the decomposition reaction of the electrolyte on the surface of the negative electrode 22 during charging and discharging of the secondary battery is suppressed, thereby achieving excellent battery characteristics and excellent safety.

[0123] In particular, if the secondary battery is a lithium ion secondary battery, a sufficient battery capacity can be stably obtained by utilizing the absorption and release of lithium, and therefore a greater effect can be obtained.

[0124] Other functions and effects of this secondary battery are similar to those of the above-mentioned electrolyte solution.

[0125] 3. Modifications The configuration of the secondary battery can be modified as appropriate, as described below. However, the series of modifications described below may be combined with each other.

[0126] [Modification 1] The above description concerns a case in which the negative electrode active material layer 22B of the negative electrode 22 contains a negative electrode active material that absorbs and releases lithium, and therefore the secondary battery is a lithium ion secondary battery that utilizes the absorption and desorption of lithium. However, although not specifically illustrated here, the secondary battery may also be a lithium metal secondary battery that utilizes the deposition and dissolution of lithium.

[0127] The secondary battery (lithium metal secondary battery) described here has a configuration similar to that of a lithium-ion secondary battery, except that the negative electrode 22 contains elemental lithium (so-called lithium metal). Specifically, the negative electrode 22 is a lithium metal foil or the like. However, the lithium metal may contain any amount of impurities.

[0128] In this secondary battery, when lithium is released in an ionic state from the positive electrode 21 during charging, lithium metal is precipitated on the surface of the negative electrode 22, and when lithium metal is eluted from the negative electrode 22 during discharging, lithium is absorbed in an ionic state in the positive electrode 21.

[0129] The method for manufacturing this secondary battery is similar to the method for manufacturing a lithium ion secondary battery, except that the negative electrode 22 contains lithium metal.

[0130] In this secondary battery, the battery capacity is obtained by utilizing the deposition and dissolution of lithium, and therefore the same effect can be obtained.

[0131] [Modification 2] A porous film separator 23 is used. However, although not specifically shown here, a laminated separator including a polymer compound layer may also be used.

[0132] Specifically, the laminated separator includes a porous membrane having a pair of surfaces and a polymer compound layer provided on one or both surfaces of the porous membrane. This is because the separator improves adhesion to the positive electrode 21 and the negative electrode 22, respectively, thereby suppressing misalignment of the battery element 20. This suppresses miswinding of the positive electrode 21, the negative electrode 22, and the separator 23, thereby suppressing swelling of the secondary battery even if a decomposition reaction of the electrolyte occurs. The polymer compound layer includes polyvinylidene fluoride or the like. Polyvinylidene fluoride has excellent physical strength and is electrochemically stable.

[0133] One or both of the porous film and the polymer compound layer may contain one or more types of insulating particles. This is because the insulating particles dissipate heat when the secondary battery generates heat, improving the safety (heat resistance) of the secondary battery. The insulating particles contain one or more types of insulating materials, such as inorganic materials and resin materials. Specific examples of inorganic materials include aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin materials include acrylic resin and styrene resin.

[0134] When a laminated separator is produced, a precursor solution containing a polymer compound and an organic solvent is prepared, and then the precursor solution is applied to one or both sides of a porous film. In this case, the precursor solution may contain a plurality of insulating particles.

[0135] Even when this laminated separator is used, the same effect can be obtained because lithium can move in an ionic state between the positive electrode 21 and the negative electrode 22. In this case, as described above, swelling of the secondary battery is further suppressed, and therefore a greater effect can be obtained.

[0136] [Modification 3] An electrolytic solution that is a liquid electrolyte is used. However, although not specifically shown here, an electrolyte layer that is a gel electrolyte may also be used.

[0137] In the battery element 20 using the electrolyte layer, the positive electrode 21 and the negative electrode 22 are wound facing each other with the separator 23 and the electrolyte layer interposed therebetween. The electrolyte layer is interposed between the positive electrode 21 and the separator 23, and also between the negative electrode 22 and the separator 23.

[0138] Specifically, the electrolyte layer contains a polymer compound together with an electrolytic solution, and the electrolytic solution is held by the polymer compound. This is because leakage of the electrolytic solution is prevented. The composition of the electrolytic solution is as described above. The polymer compound contains polyvinylidene fluoride, etc. When forming the electrolyte layer, a precursor solution containing the electrolytic solution, the polymer compound, a solvent, etc. is prepared, and then the precursor solution is applied to one or both surfaces of each of the positive electrode 21 and the negative electrode 22.

[0139] Even when this electrolyte layer is used, the same effect can be obtained because lithium ions can move between the positive electrode 21 and the negative electrode 22 via the electrolyte layer. In this case, particularly, as described above, leakage of the electrolyte solution is prevented, so that a greater effect can be obtained.

[0140] 4. Uses of Secondary Batteries Finally, uses (application examples) of secondary batteries will be described.

[0141] The use of the secondary battery is not particularly limited. The secondary battery used as a power source may be a main power source or an auxiliary power source in electronic devices, electric vehicles, etc. The main power source is a power source that is used preferentially regardless of the presence or absence of other power sources. The auxiliary power source may be a power source used in place of the main power source or a power source that can be switched from the main power source.

[0142] Specific examples of uses for secondary batteries are as follows: Electronic devices such as video cameras, digital still cameras, mobile phones, laptop computers, headphone stereos, portable radios, and portable information terminals; Storage devices such as backup power supplies and memory cards; Power tools such as power drills and power saws; Battery packs installed in electronic devices; Medical electronic devices such as pacemakers and hearing aids; Electric vehicles such as electric cars (including hybrid cars); Power storage systems such as home or industrial battery systems that store power in preparation for emergencies, etc. In these uses, one secondary battery may be used, or multiple secondary batteries may be used.

[0143] The battery pack may include a single cell or a battery pack. The electric vehicle is a vehicle that runs on a secondary battery as a driving power source, and may be a hybrid vehicle that also includes a driving source other than the secondary battery. In a home power storage system, power stored in a secondary battery, which is a power storage source, can be used to power home electrical appliances, etc.

[0144] Here, an example of the use of the secondary battery will be specifically described. The configuration described below is merely an example and can be modified as appropriate.

[0145] Figure 3 shows the block diagram of a battery pack, which is an example of an application of a secondary battery. The battery pack described here is a battery pack (a so-called soft pack) that uses a single secondary battery, and is installed in electronic devices such as smartphones.

[0146] 3, the battery pack includes a power supply 51 and a circuit board 52. The circuit board 52 is connected to the power supply 51 and includes a positive terminal 53, a negative terminal 54, and a temperature detection terminal 55.

[0147] The power source 51 includes one secondary battery. The positive electrode lead of this secondary battery is connected to a positive electrode terminal 53, and the negative electrode lead is connected to a negative electrode terminal 54. The power source 51 is connected to the outside via the positive electrode terminal 53 and the negative electrode terminal 54, and is therefore capable of charging and discharging. The circuit board 52 includes a control unit 56, a switch 57, a PTC element 58 which is a thermosensitive resistor, and a temperature detection unit 59. However, the PTC element 58 may be omitted.

[0148] The control unit 56 includes a central processing unit (CPU) and memory, and controls the operation of the entire battery pack. The control unit 56 detects and controls the usage state of the power source 51.

[0149] When the voltage of power supply 51 (secondary battery) reaches the overcharge detection voltage or the overdischarge detection voltage, control unit 56 turns off switch 57 to prevent charging current from flowing through the current path of power supply 51. The overcharge detection voltage is not particularly limited, but specifically, it is 4.20 V±0.05 V, and the overdischarge detection voltage is not particularly limited, but specifically, it is 2.40 V±0.10 V.

[0150] Switch 57 includes a charge control switch, a discharge control switch, a charging diode, a discharging diode, etc., and switches between the connection and disconnection of power supply 51 and an external device in response to instructions from control unit 56. Switch 57 includes a metal oxide semiconductor field effect transistor (MOSFET), etc., and the charge current and the discharge current are detected based on the ON resistance of switch 57.

[0151] Temperature detection unit 59 includes a temperature detection element such as a thermistor. Temperature detection unit 59 measures the temperature of power supply 51 using temperature detection terminal 55 and outputs the temperature measurement result to control unit 56. The temperature measurement result measured by temperature detection unit 59 is used when control unit 56 controls charging and discharging in the event of abnormal heat generation, and when control unit 56 performs correction processing when calculating the remaining capacity.

[0152] An embodiment of the present technology will be described.

[0153] Examples 1 to 4 and Comparative Examples 1 to 4 As will be described below, secondary batteries were manufactured, and then the battery characteristics of the secondary batteries were evaluated.

[0154] [Fabrication of Secondary Battery] In order to simply evaluate the battery characteristics, a test secondary battery was fabricated according to the following procedure: This test secondary battery was a simplified lithium metal secondary battery.

[0155] First, an electrolyte salt (lithium bis(fluorosulfonyl)imide) was added to a solvent, and the solvent was then stirred to prepare an electrolyte solution.

[0156] The solvent used was an anisole compound, 4-(trifluoromethoxy)anisole (TFMAS), and another compound, 1,2-dimethoxyethane (DME). In this case, the mixing ratio of the anisole compound and the other compound was adjusted. The content of the electrolyte salt was 2 mol / L (=1 mol / dm 3　 )

[0157] The content (wt %) of the anisole compound in the solvent, the content (wt %) of the other compounds in the solvent, and the physical properties of the anisole compound and the other compounds, namely, the boiling point (°C) and the flash point (°C), are as shown in Table 1.

[0158] For comparison, as shown in Table 1, an electrolyte solution was prepared in the same manner except that another compound, anisole (AS), was used as the solvent.

[0159] Subsequently, a lithium metal foil (thickness=0.1 mm) was pressed onto a copper foil (thickness=0.01 mm) using a press to prepare a test electrode.

[0160] Next, the electrolyte solution was dropped onto a separator (microporous polyethylene film, thickness = 10 μm) to impregnate the separator with the electrolyte solution. The amount of the electrolyte solution dropped was 0.01 ml (= 0.01 cm 3　 )

[0161] Next, a copper foil (thickness = 0.012 mm) was prepared as a counter electrode, and the test electrode and the counter electrode were laminated together with a separator impregnated with an electrolytic solution interposed therebetween, thereby completing a test secondary battery.

[0162] [Evaluation of Battery Characteristics] The battery characteristics were evaluated according to the procedure described below, and the results shown in Table 1 were obtained.

[0163] Here, the charge / discharge characteristics were evaluated as battery characteristics to examine the reversibility of the deposition and dissolution of lithium on the surface of the counter electrode, while taking safety into consideration based on the physical properties (boiling point and flash point) of the solvent.

[0164] When evaluating the charge / discharge characteristics, first, the secondary battery was charged in a room temperature environment (temperature = 23°C) to measure the charge capacity, and then the secondary battery was discharged to measure the discharge capacity.

[0165] During charging, 0.22mA / cm 2　 The battery was charged at a current density of 0.1 V for a total charging time of 3 hours.

[0166] Subsequently, the coulombic efficiency was calculated based on the formula: coulombic efficiency (%)=(discharge capacity / charge capacity)×100.

[0167] Subsequently, in the same environment, the secondary battery was repeatedly charged and discharged until the total number of cycles reached 25, while calculating the coulombic efficiency for each cycle. The charge and discharge conditions were as described above.

[0168] Finally, the average Coulombic efficiency, which is an index for evaluating charge-discharge characteristics, was calculated by averaging the 16 Coulombic efficiencies calculated for each of the 10th to 25th cycles. This average Coulombic efficiency value was rounded to one decimal place.

[0169] The nine Coulombic efficiencies calculated during the initial charge / discharge (1st to 9th cycles) are not used to calculate the average Coulombic efficiency because the Coulombic efficiency tends to vary during the initial charge / discharge. By using only the Coulombic efficiencies calculated during the later charge / discharge (10th to 25th cycles) instead of the Coulombic efficiencies calculated during the initial charge / discharge, the Coulombic efficiency is less likely to vary. This ensures the accuracy and reproducibility of the calculation of the average Coulombic efficiency.

[0170]

[0171] [Discussion] As shown in Table 1, the physical properties (boiling point and flash point) of the solvent and the average Coulombic efficiency varied depending on the type and composition of the solvent.

[0172] Specifically, when the solvent contained two other compounds (1,2-dimethoxyethane and anisole) (Comparative Example 3), the boiling point and flash temperature decreased, and the average Coulombic efficiency also decreased. In this case, the boiling point and flash temperature decreased significantly due to 1,2-dimethoxyethane, and the boiling point and flash temperature decreased due to anisole.

[0173] If the boiling point and flash point are both decreased, when the temperature of the secondary battery rises due to abnormal heat generation or the like, the secondary battery may go out of control due to excessive evaporation of the electrolyte, and the secondary battery may catch fire and burn.

[0174] When the solvent contained one other compound (anisole) (Comparative Example 4), the secondary battery could not be charged or discharged, and therefore the average coulombic efficiency could not be calculated.

[0175] In contrast, when the solvent contained one or both of an anisole compound (4-(trifluoromethoxy)anisole) and another compound (1,2-dimethoxyethane) (Examples 1 to 4 and Comparative Examples 1 and 2), the boiling point and flash point varied depending on the type of solvent, and the average Coulombic efficiency also varied depending on the composition of the solvent.

[0176] When the solvent contained only another compound (1,2-dimethoxyethane) (Comparative Example 1), the average coulombic efficiency increased, but the boiling point and flash point each decreased significantly.

[0177] The solvent contained an anisole compound (4-(trifluoromethoxy)anisole) and another compound (1,2-dimethoxyethane). Similarly, when the content of the anisole compound in the solvent was less than 30% by weight (Comparative Example 2), the average Coulombic efficiency increased, but the boiling point and flash point were both significantly lowered due to the other compound (1,2-dimethoxyethane) that accounted for the majority of the solvent.

[0178] When the solvent contained an anisole compound (4-(trifluoromethoxy)anisole) and another compound (1,2-dimethoxyethane) and the content of the anisole compound in the solvent was 30% by weight or more (Examples 1 to 4), the average Coulombic efficiency increased. In this case, the proportion of the anisole compound with a high boiling point and a high flash temperature could be sufficiently increased by relatively sufficiently reducing the proportion of the other compounds with low boiling points and flash temperatures while maintaining the average Coulombic efficiency.

[0179] When the boiling point and flash point are increased, the possibility of the secondary battery going out of control due to excessive evaporation of the electrolyte when the temperature of the secondary battery rises due to abnormal heat generation is reduced, and the possibility of the secondary battery burning due to ignition is also reduced.

[0180] Furthermore, when the average coulombic efficiency increases, the charge / discharge efficiency of a secondary battery using an electrolyte solution increases, resulting in a high battery capacity.

[0181] In particular, when the solvent contains an anisole compound and the content of the anisole compound in the solvent is 30% by weight or more, the following tendency was observed.

[0182] First, when the content of the anisole compound in the solvent was 60 wt % or more, the average coulombic efficiency was increased more.

[0183] Second, when the content of the anisole compound in the solvent was 80 wt % or less, a high average coulombic efficiency was obtained.

[0184] Third, when the anisole compound contained the compound shown in formula (2), sufficient average coulombic efficiency was obtained. In this case, when the anisole compound contained 4-(trifluoromethoxy)anisole, sufficient average coulombic efficiency was obtained, as described above.

[0185] [Summary] From the results shown in Table 1, when the solvent contains an anisole compound and the content of the anisole compound in the solvent is 30 wt % or more, a high average coulombic efficiency is obtained while the physical properties (boiling point and flash point) of the solvent are ensured. Therefore, the charge / discharge characteristics are improved while safety is ensured, and excellent battery characteristics and excellent safety are obtained in the secondary battery.

[0186] The present technology has been described above with reference to an embodiment and examples. However, the configuration of the present technology is not limited to the configuration described in the embodiment and examples, and can be modified in various ways.

[0187] Specifically, the secondary battery has been described as having a laminate film structure, but the structure of the secondary battery is not particularly limited, and may be cylindrical, prismatic, coin-shaped, button-shaped, or the like.

[0188] The battery element has been described as having a wound structure. However, the structure of the battery element is not particularly limited, and may be a stacked structure or a zigzag structure. In the stacked structure, positive and negative electrodes are alternately stacked with a separator interposed therebetween, while in the zigzag structure, the positive and negative electrodes are folded in a zigzag pattern while facing each other with the separator interposed therebetween.

[0189] Although the electrode reactant is lithium in the above description, the electrode reactant is not particularly limited. Specifically, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. Alternatively, the electrode reactant may be other light metals such as aluminum.

[0190] The effects described in this specification are merely examples, and the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

[0191] The present technology may also be configured as follows: <1> A secondary battery comprising: a positive electrode; a negative electrode; and an electrolyte solution containing a solvent, wherein the solvent contains an anisole compound represented by formula (1), and the content of the anisole compound in the solvent is 30 wt % or more. (R1, R2, and R3 are each either a hydrogen group or a halogen group.) <2> The secondary battery according to <1>, wherein the content of the anisole compound in the solvent is 60% by weight or more. <3> The secondary battery according to <1> or <2>, wherein the content of the anisole compound in the solvent is 80% by weight or less. <4> The secondary battery according to any one of <1> to <3>, wherein the halogen group includes a fluorine group. <5> The secondary battery according to any one of <1> to <4>, wherein the anisole compound includes a compound represented by formula (2). (R4, R5, and R6 each represent a hydrogen group or a halogen group.) <6> The secondary battery according to any one of <1> to <5>, wherein the anisole compound includes 4-(trifluoromethoxy)anisole. <7> The secondary battery according to any one of <1> to <6>, wherein the secondary battery is a lithium ion secondary battery. <8> An electrolyte solution for a secondary battery, comprising a solvent, wherein the solvent includes an anisole compound represented by formula (1), and wherein a content of the anisole compound in the solvent is 30 wt % or more. (R1, R2, and R3 are each either a hydrogen group or a halogen group.)

[0192] 21...positive electrode, 22...negative electrode

Claims

1. Positive electrode and, The negative electrode and, Electrolyte containing solvent and Equipped with, The solvent comprises an anisole compound represented by formula (1), The content of the anisole compound in the solvent is 30% by weight or more. Secondary battery. 【Chemistry 1】 (Each of R1, R2, and R3 is either a hydrogen group or a halogen group.)

2. The content of the anisole compound in the solvent is 60% by weight or more. The secondary battery according to claim 1.

3. The content of the anisole compound in the solvent is 80% by weight or less. The secondary battery according to claim 1.

4. The halogen group includes a fluorine group. A secondary battery according to any one of claims 1 to 3.

5. The anisole compound includes the compound represented by formula (2). A secondary battery according to any one of claims 1 to 3. 【Chemistry 2】 (Each of R4, R5, and R6 is either a hydrogen group or a halogen group.)

6. The anisole compound comprises 4-(trifluoromethoxy)anisole. A secondary battery according to any one of claims 1 to 3.

7. Lithium-ion rechargeable batteries, A secondary battery according to any one of claims 1 to 3.

8. Containing a solvent, The solvent comprises an anisole compound represented by formula (1), The content of the anisole compound in the solvent is 30% by weight or more. Electrolyte for secondary batteries. 【Transformation 3】 (Each of R1, R2, and R3 is either a hydrogen group or a halogen group.)

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